Training
Paramedics already experienced in ‘cold’ intubation (without drugs) undertook an additional 16-hour training program in the theory and practice of RSI, including class time (4 hours), practical intubating experience in the operating room under the supervision of an anesthesiologist (8 hours), and completion of a simulation-based examination (4 hours).

Methods
Patients included in the study were those assessed by paramedics on road ambulances as having all the following: evidence of head trauma, Glasgow Coma Score ≤9, age ≥15 years, and ‘intact airway reflexes’, although this is not defined or explained. Patients were excluded if any of the following applied: within 10 minutes of a designated trauma hospital, no intravenous access, allergy to any of the RSI drugs (as stated by relatives or a medical alert bracelet), or transport planned by medical helicopter. Drug therapy for intubation consisted of fentanyl (100μg), midazolam (0.1 mg/kg), and succinylcholine (1.5 mg/kg) administered in rapid succession. Atropine (1.2 mg) was administered for a heart rate <60/min. A minimum 500 mL fluid bolus (lactated Ringers Solution) was administered. A half dose of the sedative drugs was used in patients with hypotension (systolic blood pressure <100 mm Hg) or older age (>60 years).
Cricoid pressure was applied in all patients. After intubation and confirmation of the position of the endotracheal tube using the presence of the characteristic waveform on a capnograph, patients received a single dose of pancuronium (0.1 mg/kg), and an intravenous infusion of morphine and midazolam at 5 to 10 mg/h each. If intubation was not achieved at the first attempt, or the larynx was not visible, one further attempt at placement of the endotracheal tube over a plastic airway bougie was permitted. If this was unsuccessful, ventilation with oxygen using a bag/mask and an oral airway was commenced and continued until spontaneous respirations returned. Insertion of a laryngeal mask airway was indicated if bag/mask ventilation using an oral airway appeared to provide inadequate ventilation. Cricothyroidotomy was indicated if adequate ventilation could not be achieved with the above interventions. In all patients, a cervical collar was fitted, and hypotension (systolic blood pressure <100 mm Hg) was treated with a 20 mL/kg bolus of lactated Ringers Solution that could be repeated as indicated. Other injuries such as fractures were treated as required. In the hospital emergency department, patients who were not intubated underwent immediate RSI by a physician prior to chest x-ray and computed tomography head scan.

Follow up
At 6 months following injury, surviving patients or their next-of-kin were interviewed by telephone using a structured questionnaire and allocated a score from 1 (deceased) to 8 (normal) using the extended Glasgow Outcome Scale (GOSe). The interviewer was blinded to the treatment allocation.

Statistical power
A sample size of 312 patients was calculated to achieve 80% power at an alpha error of 0.05. Three hundred twenty-eight patients met the enrollment criteria. Three hundred twelve patients were randomly allocated to either paramedic intubation (160 patients) or hospital intubation (152 patients). A mean Injury Severity Score of 25 indicated that many patients had multiple injuries.

Success of intubation
Of the 157 patients administered RSI drugs, intubation was successful in 152 (97%) patients. The remaining 5 patients had esophageal placement of the endotracheal tube recognized immediately on capnography. The endotracheal tube was removed and the patients were managed with an oropharyngeal airway and bag/mask ventilation with oxygen and transported to hospital. There were no cases of unrecognised esophageal intubation on arrival at the emergency department during this study and no patient underwent cricothyroidotomy.

Outcome
After admission to hospital, both groups appeared to receive similar rates of neurosurgical interventions, including initial CT scan, urgent craniotomy (if indicated), and monitoring of intracranial pressure in the intensive care unit.

Favorable neurologic outcome was increased in the paramedic intubation patients (51%) compared with the hospital intubation patients (39%), just reaching statistical significance with P = 0.046. A limitation is that 13 of 312 patients were lost to follow-up and the majority of these were in the hospital intubation group. The authors do point out that the difference in outcomes would no longer be statistically significant whether one more patient had a positive outcome in the treatment group (P = 0.059) or one less in the control group (P = 0.061). The median GOSe was higher in the paramedic intubation group compared with hospital intubation (5 vs. 3), however, this did not reach statistical significance (P = 0.28).

More patients in the paramedic intubation group suffered prehospital cardiac arrest. There were 10 cardiac arrests prior to hospital arrival in the paramedic RSI group and 2 in the patients allocated to hospital intubation. Further detail on these patients is provided in the paper. The authors state that it is likely that the administration of sedative drugs followed by positive pressure ventilation had adverse hemodynamic consequences in patients with uncontrolled bleeding, and that it is possible that the doses of sedative drugs administered in this study to hemodynamically unstable patients were excessive and consideration should be given to a decreasing the dose of sedation.

Authors’ conclusions
The authors overall conclusion is that patients with severe TBI should undergo prehospital intubation using a rapid sequence approach to increase the proportion of patients with favorable neurologic outcome at 6 months postinjury. Further studies to determine the optimal protocol for paramedic rapid sequence intubation that minimize the risk of cardiac arrest should be undertaken.

Anaesthetist Dr Jan Persson from Stockholm has published an updated review of recent ketamine literature. The following interesting facts about our favourite drug are extracted from Dr Persson’s paper:

Action on multiple receptors earns it the nickname: ‘the nightmare of the pharmacologist’

Recently ketamine has also been shown to inhibit tumor necrosis factor-alpha (TNF- alpha) and interleukin 6 (IL-6) gene expressions in lipopolysaccharide (LPS)-activated macrophages. It has been speculated that these antiproinflammatory effects may be responsible for antihyperalgesic effects of ketamine

Ketamine can exist in two forms, or enantiomers; S-ketamine and R-ketamine. The physical properties of the enantiomers are identical, but their interactions with complex molecules, underlying PK/PD parameters, might differ. It has been well established that the elimination clearance of S-ketamine is larger than that of R-ketamine. The S-form has been commercially available for several years, probably based on the perception that it would have a better effect to side-effect ratio. The recent literature calls into question the proposed advantages of the S-enantiomer.

Ketamine has been shown to induce neuroapoptosis, or neuronal cell death, in newborn animals. This is obviously a concern in paediatrics, where ketamine plays an important role, both in anaesthesia and for sedation/analgesia during painful procedures. The relevance in humans of these effects, however, is unclear, and as pointed out by Green and Cote it does seem unlikely, for various reasons, that such an effect would be of major importance. It does not seem likely, though possible, that a clinically relevant effect would have passed unnoticed.

Another, somewhat unexpected, side effect that has emerged in recent years is bladder dysfunction. In some cases the bladder effects progress to ulcerative cystitis. Although the reported cases have mainly concerned recreational drug users, they are relevant for long-term analgesic use as well. The mechanisms involved are unknown. This side effect might turn out to be the most serious limitation to long-term analgesic treatment with ketamine.

Seventy doctors and nurses from neonatal units administered positive pressure ventilation to a term newborn manikin using a Neopuff T-piece device. Recordings were made (1) before training, (2) after training in mask handling and (3) 3 weeks later. Leak and obstruction were calculated.

Median (IQR) leak was 71% (32–95%) before training, 10% (5–37%) directly after training and 15% (4–33%) 3 weeks later (p<0.001). When leak was minimal, gas flow obstruction was observed before, directly after training and 3 weeks later in 46%, 42% and 37% of inflations, respectively.

The training provided included the following demonstrated mask technique:

Place the manikin’s head in a neutral position and gently roll the mask upwards onto the face from the tip of the chin.

Hold the mask with the two-point-top hold where the thumb and index finger apply balanced pressure to the top flat portion of the mask where the silicone is thickest.

The stem is not held and the fingers should not encroach onto the skirt of the mask.

The thumb and index finger apply an even pressure on top of the mask.

The third, fourth and fifth fingers perform a chin lift with the same pressure upwards as applied by the thumb and index finger downwards.

In this technique the mask is squeezed onto the face, between the downward thrust of the fingers and upward pull of the chin lift.

Even with the right technique, adequacy of ventilation can be hard to assess. Principles to bear in mind are:

International guidelines recommend that infants with inadequate breathing or bradycardia be given positive pressure ventilation (PPV) via a face mask with a self-inflating bag, flow-inflating bag or T-piece device.

Adequacy of ventilation is then judged by assessing the heart rate.

However, if the heart rate does not increase, chest wall movements should be assessed to gauge adequacy of ventilation.

A human observational study reported a mean VT of 6.5 ml/kg in spontaneous breathing preterm infants in the first minutes of life.

When assisted ventilation is required, a peak inflating pressure (PIP) is chosen with the assumption that this will deliver an appropriate VT.

However, lung compliance and therefore the PIP required to deliver an appropriate VT vary in the minutes after birth.

It is likely that there are even greater differences between infants as the mechanical properties of the lung vary with gestational age and disease states.

In addition, many infants breathe during PPV adding to the inconsistency of VT delivered with a set PIP. Therefore, relying on a fixed PIP and subjective assessment of chest wall movement may result in either under- or over-ventilation.

Animal studies have shown that PPV with VT >8 ml/kg or inflations with large VTs can damage the lungs.

In an observational study of actual newborn resuscitations in Melbourne, researchers measured inflating pressures and VT delivered using a respiratory function monitor, and calculated face mask leak. After 60 seconds of PPV, resuscitators were asked to estimate VT and face mask leak. These estimates were compared with measurements taken during the previous 30 s.

In 20 infants, the median (IQR) expired tidal volume (VTe) delivered was 8.7 ml/kg (5.3–11.3). VTe and mask leak varied widely during each resuscitation and between resuscitators, who were also poor at estimating VT and mask leak.

Drowning is one of the leading causes of accidental death in children. Some apparent drownings may be related to sudden cardiac death, in particular to unidentified channelopathies, which are known to precipitate fatal arrhythmias during swimming-related events.

The majority of cases of sudden cardiac death in children and adolescents are secondary to either hypertrophic or right ventricular cardiomyopathy with coronary artery abnormalities also prevalent, and reports have demonstrated these cardiac abnormalities on autopsy following sudden swimming-related deaths.

The gene deletion in LQT1 (KCNQ1) leads to a reduction in the repolarising potassium current (IKs) and prolongation of repolarisation. This lengthens the QT interval (which may be lengthened further by facial immersion in cold water). A premature ventricular contraction (PVC) again which may be initiated by swimming occurring during the vulnerable part of repolarisation leads to establishment of polymorphic ventricular tachycardia (torsades de pointes).

The ryanodine receptor gene mutation (RyR2) in catecholaminergic polymorphic ventricular tachycardia leads to defective closure of the receptor on the surface of the sarcoplasmic reticulum during diastole. This leads to increased calcium (Ca2+) leakage from the sarcoplasmic reticulum and increased potential for delayed afterdepolarisations and subsequent ventricular tachycardia.

Some recommendations are made in an article in Archives of Disease in Childhood:

Asphyxiation by an inhaled foreign body is a leading cause of accidental death among children younger than 4 years. A review article examining 12,979 paediatric bronchoscopies made the following observations:

Epidemiology

Most aspirated foreign bodies are organic materials (81%, confidence interval [CI] = 77%-86%), nuts and seeds being the most common.

The majority of foreign bodies (88%, CI = 85%-91%) lodge in the bronchial tree, with the remainder catching in the larynx or trachea.

The incidence of right-sided foreign bodies (52%, CI = 48%-55%) is higher than that of left-sided foreign bodies (33%, CI = 30%-37%). A small number of objects fragment and lodge in different parts of the airways.

A history of a witnessed choking event is highly suggestive of an acute aspiration.

A history of cough is highly sensitive for foreign body aspiration but is not very specific. On the other hand, a history of cyanosis or stridor is very specific for foreign body aspiration but is not very sensitive.

End expiratory film: delayed emptying of the left lung suggests local air trapping

Anaesthetic considerations

Preoperative assessment should determine where the aspirated foreign body has lodged, what was aspirated, and when the aspiration occurred (“what, where, when”).

The choices of inhaled or IV induction, spontaneous or controlled ventilation, and inhaled or IV maintenance may be individualized to the circumstances. Although several anesthetic techniques are effective for managing children with foreign body aspiration, there is no consensus from the literature as to which technique is optimal.

An induction that maintains spontaneous ventilation is commonly practiced to minimize the risk of converting a partial proximal obstruction to a complete obstruction.

Controlled ventilation combined with IV drugs and paralysis allows for suitable rigid bronchoscopy conditions and a consistent level of anesthesia.

Close communication between the anesthesiologist, bronchoscopist, and assistants is essential.

Chest x-rays often miss pneumothoraces in the trauma room. These are occult pneumothoraces. A study using agreement by two fellowship trained radiologists as the gold standard for CXR interpretation showed that 80% of these were truly occult, ie. not detectable by the radiologists from CXR and only demonstrable on CT. Of those seven cases that could or should have been identified by emergency physicians (ie. ‘missed’ pneumothoraces) subcutaneous emphysema (5), pleural line (3), and deep sulcus sign (2) were detected by the radiologist reviewers.

This serves both as a reminder of the signs to look for on CXR for pneumothorax, and of the inadequacy of plain radiography in trauma patients. The authors advise in their discussion that ‘Thoracic ultrasonography may be the ideal diagnostic modality as it has a high sensitivity for the detection of PTX and it may be performed quickly at the bedside while maintaining spinal precautions’.

If you don’t know how to detect a pneumothorax with ultrasound yet, have a look here.

Helicopters are controversial in EMS circles, particularly in the United States, which seems to have a high number of Helicopter Emergency Medical Services (HEMS) crashes. Although this may in part be a reflection of a large increase in HEMS missions, and the factors contributing to crash fatalities have been studied, it makes sense to limit HEMS missions to those that are likely to make a difference to the patient. Advantages of HEMS services may include the ability to deliver a patient more rapidly to the most appropriate facility, as well as being able to convey a highly skilled team more rapidly to the scene.

Analysis of patients from the National Trauma Databank identified 258,387 subjects transported by either helicopter (HT) (16%) or ground ambulance (GT) (84%). HT subjects were younger (36 years ± 19 years vs. 42 years ± 22 years; p < 0.01), more likely to be male (70% vs. 65%; < 0.01), and more likely to have a blunt mechanism (93% vs. 88%; < 0.01) when compared with GT subjects.
For every dead-on-arrival (DOA) subject in the HT group, there were 498 survivors compared with 395 survivors for every DOA subject in the GT group. When comparing indicators of injury severity, patients transported by helicopter were more severely injured (mean ISS and percentage with ISS > 15), were more likely to have a severe head injury, and were more likely to have documented hypotension or abnormal respiratory when compared with those transported by ground ambulance. Furthermore, HT subjects also had longer length of stay, higher rates for ICU admission, and mechanical ventilation, as well as an increased requirement for emergent surgical intervention.

interestingly, this study shows that <15% of HT patients nationally are discharged within 24 hours. This is much lower than the 24.1% reported previously, suggesting that the degree of over-triage may not be as significant on the national level as reported in smaller studies.

Evidence-based medicine reminds us to beware ‘experts’. However, here’s one self-described expert who talks some sense. Doctor (Doktor?) HJ Priebe from the University Hospital Freiburg in Germany suggests the risk of harm outweighs the risk of benefit from this procedure:

‘Despite the lack of evidence for its effectiveness and evidence for numerous deleterious effects, cricoid pressure is still considered a standard of care during rapid sequence induction, and its application is considered mandatory in patients at high risk for gastric regurgitation. However, by using cricoid pressure, we may well be endangering more lives by causing airway problems than we are saving in the hope of preventing pulmonary aspiration. It is dangerous to consider cricoid pressure to be an effective and reliable measure in reducing the risk of pulmonary aspiration and to become complacent about the many factors that contribute to regurgitation and aspiration. Cricoid pressure is not a substitute for optimal patient preparation. Ensuring optimal positioning and a rapid onset of anesthesia and muscle relaxation to decrease the risk of coughing, straining or retching during the induction of anesthesia are likely more important in the prevention of pulmonary aspiration than cricoid pressure.

‘At the time of Sellick’s description of the technique of cricoid pressure, morbidity and mortality from pulmonary aspiration during the induction of anesthesia in the surgical population in general, and the obstetric population in particular, were of great concern. At that time, the concept of cricoid pressure was highly attractive. However, during the past 48 years, many aspects of anesthetic management have considerably changed, and knowledge has advanced. By today’s standards, cricoid pressure can no longer be considered an evidence-based practice. This is why more and more anesthetists (including myself) no longer apply cricoid pressure.‘

Just as well really, because these guys show many people don’t know how to do it anyway! Cases were identified in which pressure was mistakenly applied to the thyroid cartilage and even the sternocleidomastoid muscles!Variable application and misapplication of cricoid pressure J Trauma. 2010 Nov;69(5):1182-4

The complication rate after a negative or nontherapeutic laparotomy is reported to be substantial but most of this reported morbidity is because of associated injuries and is not related to the abdominal exploration. On the other hand, the morbidity and mortality associated with a delay in taking the injured patient to the operating room is well recognised. A retrospective study attempts to show that when injury severity (using TRISS) is controlled for, negative laparotomy did not significantly increase the complication burden compared with no laparotomy in blunt abdominal trauma patients.